What is the difference between a simple device and complex device in intrinsic safety?

Intrinsic safety is premised on limiting the electrical and surface heat energy of a product to a level below the ignition energy of the flammable atmosphere. To do so, the operational characteristics of the field device, the intrinsically safe barrier and the wire itself must be evaluated to ensure that the circuit energy does not exceed the ignition energy required to ignite the flammable atmosphere. This is done by resolving the entity parameters defined for the field device, the barrier and wire being used.

Simple devices, as they are known, do not incorporate sufficient energy to impact the safety of an IS circuit and as such, do not have entity parameters.  Examples include discrete switches, wire terminals, resistors and RTDs and some LED indicator applications. The product standards for intrinsic safety define the energy threshold as 1.5V, 100mA and 25mW. If a device meets this criteria, it may be added or subtracted from the circuit without impacting the explosion safety of the circuit.

Simple devices still require a product certification mark but do not need to incorporate hazardous location markings.   All other field devices that exceed the simple device criteria are defined as “non-simple” or complex devices. Such devices will impact the energy within an IS circuit and must be certified and marked with appropriate hazardous location product markings. 

Want to learn more about the application of intrinsic safety in hazardous locations? Consider enrolling in the EngWorks Online Hazardous Locations Fundamentals Course. We discuss intrinsic safety in detail and how is can be applied for equipment protection in a classified location.  Also check out our free HazLoc supermini course. It guides you through evaluating the markings on hazloc products for use in Canadian installations.

Go to: https://onlinecourses.engworks.ca/ Save 20% on the course list price of $495 until the end of November.